The singer and Burlesque star threw a party at her Beverly Hills home on New Year's Eve, with 175 guests, including her new man Matt Rutler and celeb pals and newlyweds Nicole Richie and Joel Madden.
Aguilera – who toasted the New Year with a custom bottle of Moët champagne with her name engraved on it – wowed the crowd in a silver sequin Herve Leger dress and jeweled Christian Louboutin heels. "She was so excited!" a guest tells PEOPLE. "She was all smiles all night and really relaxed. She's had a tough year, but she looked genuinely happy."
A New DirectionIndeed, the singer recently confided her anticipation of the event in an interview with PEOPLE. "This party is all about counting down to the new chapter of my life," she said. "I'll be surrounded by friends and family who care and love me to death."
With the party and the kick off of 2011, she's closing the book on a difficult year in which she filed for divorce from her husband Jordan Bratman.
"It's really a time for me to look forward to the next chapter in my life," Aguilera added. "I couldn't think of a better way to bring in the New Year [than with a party]."
Courtesy 2me Studios
As for hitting the big 3-0, Aguilera says she has no worries on growing older.
"Everything is exciting right now," she says. "I'm an actress and I'm a single mom. I'm entering my thirties. I'm looking at this as an exciting new chapter in my life."
If the eve of the New Year is anything to go by, she's looking at a good year ahead, according to one guest. "At midnight, she got up on stage and thanked everyone for coming. She told everyone how excited she was about the new year, and how normally New Year's Eve parties are usually a disappointment, but this year she wanted all her friends to have a really fun night. And it was! It was a great party."